The dynamic, context dependent nature of the cortical processing of visual information will be explored as the basis for the integration of the visual image into contours and surfaces, for perceptual learning, and for the top down influence of attention on early level visual processing. Our approach will be to do parallel psychophysical and physiological studies to establish a correlation between the response properties of cells in visual cortical areas V1 and V2 and the perceptual characteristics of intermediate level vision. We will examine the nature of facilitatory and inhibitory lateral interactions in contour integration and surface segmentation, and will explore the role of depth cues in these processes. Experience plays an important role in our ability to discriminate stimulus attributes and in the recognition of stimulus configuration, and we will explore the mechanism of this by studying the effect of perceptual learning on contextual interactions. To explore the role of top down influences on early levels of visual processing we will determine the dependency of the response properties of cells on the discrimination task being performed, and will explore the role of attention in modulating contextual interactions. These studies will help in understanding the mechanism of functional compensation after retinal and visual cortical lesions, of visuospatial integration and of the role of experience in early visual processing.